The present inventions relate to improvements in robotic technology used in the oil and gas industry to significantly reduce oil and gas operational costs, especially in deep wells. More particularly the present inventions relate to the use of programmable tools permanently located downhole in a well and which can on demand perform various downhole tasks in the wells such as, for example, resetting safety valves, adjusting flow control devices; setting and removing downhole devices; measuring well parameters at various locations and condition, and retrieving measurement and performance data.
During the wellbore completion phase of wells, a rig is normally present at the wellhead. Occasionally, the large drilling rig is removed and a small work rig is erected to perform completion operations. However, many operations during the completion phase could be performed without the use of a rig if a mobile platform robotic device could be utilized to move into position in the bottom hole assembly in the wellbore, especially in the horizontal sections of the wellbores. Wells usually continue to produce hydrocarbons for many years. Various types of operations are performed during the life of producing wells. Such operations include removing, installing and replacing different types of devices including fluid flow control devices, sensors, packers or seals; performing remedial work including sealing off zones, cementing, reaming, repairing junctures, milling and cutting; diverting fluid flows, controlling production from perforated zones; activating sliding sleeves, testing wellbore production zones or portions thereof, and making periodic measurements relating to wellbore and formation parameters. During the production phase or workover or testing operations, a rig is especially erected at the well site prior to performing many of these operations. Using conventional rig operations can be time consuming and expensive. The primary function of the rig in some of such operations is to convey, position and orient tools to the desired work site. A mobile platform robotic device that can move and position tools at the desired work site can allow the desired downhole tasks to be performed without requiring a rig and bulky tools and tool handling systems.
Mobile platform robotic devices tethered to the surface by wirelines or coil tubing are used in vertical and horizontal well operations. These devices sometimes called tractors can move in the well using various forms of traction devices. In deep wells, the use of a tether requires the tractor to generate excessive force as the distance increases to pull the tether. In extended downhole distances, time is consumed in moving the devices to location. Some tethered tractors carry a self-contained battery powered tractor unit that will disconnect from the tethered tractor to extend the operation range by performing downhole operations without a tether. Typically, communication systems are used to connect the untethered tractor to the tethered tractor. Examples of these units can be found in the U.S. Pat. Nos. 5,947,213; 6,026,911 and 6,112,809 owned by Intelligent Inspection Corporation. The disclosures of these patents are incorporated herein for all purposes.
While the proposed use of a detachable untethered unit can provide tool access to otherwise unreachable well locations it does not solve the problems associated with the time and expense required in moving to these remote locations. When repeated or regular downhole operations are required in deep wells, moving the tractor units to and from the surface is unacceptable and uneconomical.
The present inventions relate to using an electro-mechanical tractor that docks at a downhole docking station from which it exits, moves within the well to perform tasks and then returns to the docking station. Wells to which these inventions pertain, comprise all wells having subterranean portions. Although the present inventions have particular advantages when applied to deep locations in wells, the term downhole is used to include any location spaced from the wellhead. Down and up in this regard refer to a direction along the well toward the wellhead and away from the wellhead even though the actual portion of the well may not be vertically upright. Wellhead or surface includes both land and sub sea locations and in the latter case can refer to the seabed or water surface. Preferably, conductors connect the docking station to the surface for conveying power and control information. These conductors could be either embedded in the tubing wall or separate. The described examples use a docked tractor to move out into the well to mechanically open and close a subsurface safety valve or sliding sleeve valve as needed.
The task of operating the safety valve is just one operation that can be performed at these remote downhole locations without requiring the time consuming procedure of opening the well and moving the tractor assembly from the surface to the remote downhole location. These tasks could be as varied as removing, installing and replacing different types of devices including fluid flow control devices, sensors, packers or seals; performing remedial work including sealing off zones, cementing, reaming, repairing junctures, milling and cutting; diverting fluid flows, controlling production from perforated zones; activating, resetting and adjusting valves such as safety valves and sliding sleeves, testing wellbore production zones or portions thereof, making periodic measurements relating to wellbore and formation parameters, setting plugs remotely, or retrieving pressure temperature recording devices and uplink data to the surface via electronics located either onboard the tractor or in the docking station. As used herein the term tasks is used in its broadest generic sense to include all well operations.
More particularly, the tractor tool assembly could move from a downhole docking station to a valve and engage the valve and perform the task of opening, closing or adjusting it. In the safety valve embodiment the tractor could have a tool that locks into a profile on the safety valve""s flow tube and then the tractor would extend against the tubing wall and telescope, forcing the valve to the open position. When the flow tube reaches the valve open position, a mechanical or electrical powered lock or latch engages and holds the flow tube in the open position. In this embodiment, the remote controlled tool then disengages from the valve and retreats to the docking station.
The docking stations in the disclosed embodiments are in the form of a side pocket mandrel assembled in the production tubing. As used herein docking means or tractor docking station includes any location downhole in the well where the tractor can reside in the well when not in use. In tractors whose profile causes minimal flow restrictions docking in the main wellbore itself is possible, in other cases it is preferable for the tractor to be docked in a side pocket mandrels or branching bores out of the wellbore. Preferably, the docking means provides a source of power for the tractor either in the form of a conductor or receptacle for recharging batteries onboard the tractor. Various embodiments of means for supplying electrical power to the docking station are envisioned, including conductors extending to the surface, rechargeable or chemical batteries, and downhole electrical power generators. The tractor is operably associated with the docking station, in that, it receives power from the docking station allowing it to remain downhole indefinitely and perform repeated tasks without leaving the well tubing. In some embodiments, the tractor is also operably associated with the docking station by receiving its operating instructions from the docking station either by hardware or wireless means. In this invention, the remote controlled tractor and the valve assembly are all in direct, intimate contact with the wellbore fluid, and thus are inherently pressure balanced with wellbore fluid pressure. This feature makes the performance of the valve insensitive to setting depth.
The tractor could be powered by onboard batteries that are charged when the tractor is docked. In that position, the tractor could engage an electrical socket that would charge the batteries when the tractor is in the stowed position. The tractor could be signaled by a spooled control wire or could be wireless. The tractor could be programmed to travel a certain distance then seek the profile and engage it. Once full stroked, the tractor could disengage the profile and crawl back home or be flowed back into the docking station. Once in the docking station, the tractor would plug into the power socket to be charged for the next cycle. Alternatively, the tractor could drag a power and control conducting tether from the docking station to the task location. The tether could be mechanically retractable (spooled) to quickly return the tractor to its docking station.
The term tractor means or tractor assembly means is used to refer to a self propelled device that can move about the wellbore without mechanical connection to the well surface and includes but is not limited to the particular tractor and robots described herein directly and by reference. The means for moving the tractor about the wellbore can include wheels, endless tracks, articulating inchworm type devices, propellers, cable-spool assemblies and the like. The moving means can be powered by solenoids, actuators, motors and other electrically operable means or hydraulically operated via electrical control devices. Means for performing tasks on the tractor can be a manipulateable arm, rotating device or the like. Each tractor has a means for controlling the movement means and task performing means which can comprise a programmable computer on the tractor or remote from the tractor.
A variety of tools could be stored downhole in tool stations and picked up and used by the tractor means as required to perform the desired task.
As such, these tractors could be individually addressable by wire or wireless commands to perform various tasks. Means for communicating with the tractor is provided and includes both wire and wireless communication links. Wireless includes electromagnetic, optical, acoustic, and pressure transmissions.
Therefore it may be seen that an array of tractors could be located within a wellbore and associated laterals to perform a diversity of tasks.